Conventional data processing systems, especially multiprocessor systems, allocate access to the shared system bus coupling the various bus devices to system memory through a mechanism whereby individual bus devices each control access to the system bus. Typically, each bus device will queue it's individual bus requests for various operations internally. Then, each bus device makes the determination of which of the various operations it wishes to perform on the system bus by sending the appropriate corresponding bus request to the system controller. Thus, each individual bus device determines internally which of its bus requests has higher priority. The system controller is then required to arbitrate between the received bus requests from the individual bus devices.
One disadvantage of this arbitration mechanism is that a portion of the decision process for accessing the various resources coupled to the system bus is delegated to each of the bus devices. As a result, the system controller is only able to view a portion of all of the various requests from the individual bus devices, since each of the individual bus devices retains and queues a significant number of bus requests. Thus, there is a need in the art for a more efficient arbitration mechanism for granting access to the system bus.